The present invention relates to a method and apparatus for quickly and accurately determining the amount of metal to be removed from the lower portion of an engine block when the engine is to be stroked, i.e. have a longer, replacement, connecting rod installed to increase the engine""s cylinder displacement.
Although there are many and varied methods for boring an engine block such as those disclosed in U.S. Pat. Nos. 4,451,186, 4,652,186, 4,789,279, 4,213,721, 6,012,880, 5,865,573 4,871,285, and the like; and for boring overhead cam engine cylinder heads, 5,836,725, 5,655,278 and the like, all of which are incorporated herein by reference, there is no method or apparatus in the prior art for determining the amount of metal to be removed from the lower portion of an engine block when the engine is to be stroked, other than trial and error.
The trial and error method of stroking an engine involves removing metal from each side of the lower portion of the block, installing the crankshaft, installing longer connecting rods, and then rotating the crankshaft to determine if enough metal has been removed from the block to allow crankshaft rotation with the longer rods without contact by the rods on either side of the block""s lower portion. A connecting rod longer than the original rod requires a relatively greater open area in the lower engine block in order to rotate as compared to the open area provided in the original engine block for the original connecting rod. The prior art method involved numerous trial assemblies, much labor and time. It also made necessary the complete washing of the block and the parts after each assembly in order to insure that no loose metal remained on the rod-crankshaft surfaces and the crankshaft-block surfaces. There was also the possibility, when using the prior art trial and error method, of removing too much metal from the block, exposing a portion of the water jacket in the block and effectively destroying the block.
The present invention is a method and apparatus to quickly and accurately determine the amount of metal required to be removed from the lower portion of an engine block when the engine is to be stroked.
The apparatus of the present invention includes a first cylindrical member, a spacer or stroker bar, and a connector means for connecting the first cylindrical member, the spacer bar, and a first end of a piston connecting rod to be tested, wherein the spacer bar is positioned between the first cylindrical member and the piston connecting rod so as to center the connecting rod within a cylinder when the first cylindrical member is placed in a crank position, and wherein the first cylindrical member has a central hole which provides for rotatable movement of the spacer bar.
In another embodiment, the apparatus includes a cylindrical member, a spacer bar, a first connecting means for connecting the first portion and the spacer bar, and a second connector means for connecting the spacer bar to a first end of a piston connecting rod to be tested.
In yet another embodiment, the apparatus further includes at least one piston simulator which is connected to a second end of a piston connecting rod to be tested to align and center the connecting rod within the cylinder bore.
The present invention also concerns a method for determining the amount of metal to be removed from a stroked engine block. The method includes placing the first cylindrical member of the device described above into a crank position of an engine block, attaching to a spacer bar for movement of the spacer bar and attaching for movement to an end of the connecting rod to be tested, inserting the piston connecting rod under test into a piston cylinder, and then rotating the device in a reciprocal manner to determine whether the piston connecting rod under test contacts the engine block and if so, to thereby determine the amount of metal to be removed from the block.